An assay system for monitoring functional fibrinogen in patients undergoing thrombolytic therapy will be developed. This system will be based on a novel dry reagent assay technology which has recently been applied successfully to PT and activated PTT tests. Introduction of a rapid convenient fibrinogen assay system on a decentralized basis could provide accurate results sooner than existing laboratory methods and could serve as an important diagnostic guide in thrombolytic therapy. We propose to develop this fibrinogen assay system and to assess its potential using a combination of laboratory studies of influencing factors and clinical sample studies. Application to early determination of low fibrinogen levels in thrombolytic therapy patients will be explored. This work will be performed in conjunction with Duke University Medical Center. Phase I support would fund assay development activities and comparison with reference methods.